HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New Millenniumsimple linear equations to more sophisticated theoretical expressions.The main purpose of the model is to provide an estimate of the relativitybetween the manipulated variable and the intermediate and performancevariables. When the manipulated variables are perturbed by themaximization algorithm, an estimate of the change in the intermediateand performance variables with relation to the constraint values must bemade.The optimization or maximization algorithm can also be simplisticor sophisticated. There is an advantage to using the simpler approach.The procedure always starts with a known solution. Then, the perturbationprocedure takes advantage of what a digital computer does best,simple calculations repeated over and over. In sophisticated optimizationalgorithms, there may be multiple solutions and the real solutionsmust be selected.In general, the computers used for supervisory control aremultitasking computers which are interfaced with the DCS through acomputer gateway (Figure 3-6). The data which reside in control mod-Figure 3-6. Gateway for DCS.©2001 by The Fairmont Press, Inc. All rights reserved.